Not all sensors are created equal. Some level transmitters have distinct advantages that give them access to applications where other sensors are unable to perform.
In past blog posts we have discussed a variety of application obstacles. They include things like high temperatures, foam, vapor, and turbulence. Today, we would like to cover some level sensors that can monitor harsh chemicals.
To be fair, “harsh” chemicals in the level measurement world can mean any liquid that is tough to measure for a variety of reasons (including those obstacles listed above). However, for this discussion, we will define a harsh chemical as being a liquid substance that has a knack for attacking popular instrument materials.
For example, many chemicals out there are not compatible with plastics like polyurethane or polypropylene. So if you were to install a cable suspended float switch or submersible pressure transmitter with a polyurethane cable into a tank full of Xylene, your sensor will eventually be destroyed.
The more remote the chemical tank, the more critical sensor selection becomes. You can add communications to just about any sensor, but you may not be able to respond quickly to a corroded sensor and a leaking tank.
One of the best ways to measure harsh chemicals is to use a level transmitter that does not come in contact with the chemical such as an ultrasonic level sensor or radar level sensor.
While these two level sensors are often a great fix for avoiding chemical compatibility issues, they may still be susceptible to other measurement obstacles.
For ultrasonic sensors, this includes foam and thick vapors. It is not uncommon for harsh chemicals to have these characteristics.
On the other hand, while radar sensors may overcome foam and vapors, the effort required to fine-tune them to ignore these hindrances can be extensive. And, not to mention, the big price tag associated with radar transmitters can be, well, BIG.
Even if there aren’t other obstacles affecting your non-contact level transmitter, the chemical can still damage the sensor through splashing and vapors.
Since non-contact sensors come with another set of disadvantages, it is sometimes easier to go back to a contacting level transmitter.
316L stainless steel is compatible with many common chemicals where plastic materials are not. For this reason, we have quite a few customers that prefer to use a resistive chain level or magnetostrictive probe. On these units, you can guarantee that the only material that will contact the chemical will be 316L stainless.
For that small set of chemicals that refuses to play well with 316L stainless steel or plastics, a coated probe level transmitter can be the answer to your really specific "How do I measure this stuff?"
While using a compatible probe can overcome most chemical compatibility issues, it is not always the easiest to install. If you have a tall tank, these probes can be very long and heavy, requiring special equipment to transport and install them - another problem that gets worse with a remote tank. Unless you use a flexible stem probe, like APG's new MPXI-F, with our proprietary-blend-PVDF stem material. Not only is it compatible with most chemicals, it's flexible enough to considerably reduce shipping and installation costs.
So if you are looking for a sensor that is:
then you will want to consider a pressure sensor as your level transmitter.
Many tanks will come with a valve at the bottom of the tank. By installing the pressure sensor directly on a ball valve at the bottom of the tank, the sensor will measure the amount of pressure being exerted on it by the weight of the liquid in the tank just like a submersible pressure transducer. But, instead of having the sensor and cable inside the tank and exposed to the chemical, only the stainless steel process fitting and diaphragm will come in contact with the chemical.
In other words, this type of level transmitter is often the best for measuring harsh chemical levels in a tank.
Too often, we replace sensors that have been installed in the wrong applications. This is one of the most common complaints we hear over the phone. So before you make any rash sensor decisions, consider a few different technologies. Think even harder if this sensor will be installed on a remote tank.
It’s no secret that pressure sensors are installed on a lot of tanks to monitor the tank level. That’s because it works – even if it’s not as shiny as a radar sensor (speaking figuratively, of course, as pressure sensors probably are shinier due to their steel construction). It should also not be a secret that a few of our best pressure transducers now work with our Tank Cloud remote monitoring solution.
If you have any questions on this strategy or have some other tips on overcoming harsh chemicals - especially in remote locations - feel free to contact us.
